As it is known by the man skilled in the art, image stabilization algorithms have been proposed in order to remove unwanted camera movements or jitter while preserving the requisite camera movements, thus providing a more pleasant viewing experience. One means here by “unwanted camera movement or jitter” all the undesired positional fluctuation of an image, such as translation and/or rotation, which are added to the intentional motion of the camera.
In most of the digital image stabilization (or DIS) algorithms, three main steps are successively applied to the digital images of a video sequence. The first step consists in determining the motion estimation between two consecutive image frames (at time t and (t−1)) of the video sequence. The second step consists in determining the jitter of each image frame from the corresponding determined motion estimation. The third step consists in filtering (removing) the jitter from global motion parameters of each image frame in order to remove the unwanted motion(s).
Examples of such digital image stabilization algorithms are notably described in the patent documents US 2003/0090593 and US 2004/0001147. The first and third steps of these known digital image stabilization algorithms are easy to implement. Difficulties occur in the second step which aims at separating the unintentional motion(s) from the intentional one(s). Because of these difficulties, the algorithms offer either a weak stabilization of the static or quasi-static video sequences and a good (effective) following of panoramic/traveling video sequences, or a strong (effective) stabilization of the static or quasi-static video sequences and a jerky panoramic/traveling video sequences.